In a speech to his party’s spring conference in Caernarfon, he said he was ready to take on the responsibility to govern Wales.

Mr Jones used his speech to champion Plaid’s policy platform, contrasting it with Labour’s “negative” campaign.

He praised Plaid’s record as the Assembly’s biggest opposition party, saying it had taken tough decisions and extracted a series of concessions from Rhodri Morgan’s minority administration.

The Labour Party had “destroyed” people’s trust in politics and it was up to Plaid to rebuild it, he said.

In a newly-honed conversational style, Mr Jones wandered around the stage, delivering long tracts of his speech without notes.

He said Plaid faced one of the most important elections in its history.

The party says it is in upbeat mood as it seeks to oust Labour at May’s election and make up for the disastrous 2003 poll when it lost five seats.

Labour has sought to challenge Plaid over independence, which it holds as a “long-term ambition” for Wales, and is warning a vote for anyone but Labour will create a Tory-led coalition government.

Mr Jones said: “We will be offering them (voters) the politics of hope and ambition and Labour will be offering the politics of fear.

“We will be offering a new kind of politics, a different kind of politics to restore people’s trust in the political system and Labour will reinforce the destructive cynicism of the last 10 years.”

He added: “We have to move now from being the main opposition in the Assembly to take the responsibility to govern Wales.”

Referring to Plaid's campaign slogan - "Make a difference'' - Mr Jones said: `"We are now on the threshold of one of the most important elections in the party's history and when you go out to ask people to vote for Plaid Cymru during the next 40 days, I want you to tell them that this party is ready to take on the responsibility of governing Wales because we are prepared to make a real difference to their lives.''

He listed the seven flagship policies that Plaid has so far unveiled: affordable childcare; laptops for 11-year-old pupils; repaying the first five years student loans of graduates who stay in Wales; first-time home-buyers’ grants of up to #5,000; business rate cuts for small firms; a new community health service; and a 3% annual cut in carbon emissions.

Despite Plaid’s insistence that they are all affordable, rival parties have claimed these spending pledges are unrealistically expensive.

Mr Jones also referred to a promise to cap pensioners’ council tax bills so they do not rise faster than inflation.

In an attack on Labour’s record, he said Wales had slipped down the UK wealth league despite #5 billion being invested in the economy since 1999.

He mentioned the “scandal” of the NHS withholding money for patients’ operations and said universities were not being funded properly.

“They have worn Margaret Thatcher’s clothes very well, haven’t they, over the last 10 years?” he said.

The cash-for-honours saga and the war in Iraq had exhausted people’s confidence in the political process.

Mr Jones said governing Wales was the “next step” in his party’s 80 years of fighting elections.

“We are a confident party. We are a professional party, ready now to go out and ensure people in Wales know what the policy programme of Plaid Cymru is for the Assembly election,” he said.